1. Field of the Invention
An aspect of the present invention relates to an information storage medium including a plurality of recording layers, and more particularly, to an information storage medium, i.e., an optical disk, including a dedicated area for a predetermined purpose in an outer circumferential area thereof, and a recording/reproducing apparatus and method.
2. Description of the Related Art
Optical disks are information storage mediums widely used in optical pick-up devices, which record/reproduce information in a contactless manner. Optical disks are divided into compact disks (CDs) and digital versatile disks (DVD) according to data recording capacity. Optical disks that can be recorded, deleted, and reproduced include 650 MB CD-Rs, CD-rewritables (RWs), 4.7 GB DVD+R/RWs, DVD-random access memories (RAMs), and DVD-R/RWs. Optical disks dedicated for data reproduction include 650 MB CDs and 4.7 GB DVD-ROMs. Further, next-generation DVDs having recording capacity of 15 GB or greater are under development.
FIG. 1A illustrates the structure of a conventional rewritable optical disk. FIG. 1B illustrates the structure of a conventional optical disk for data reproduction. A lead-out area and a lead-in area of the rewritable optical disk illustrated in FIG. 1A are almost identical. The lead-in area of the rewritable optical disk illustrated in FIG. 1A includes a control data zone where information regarding the rewritable optical disk and copy protection is pre-recorded. A rewritable area of the lead-in area includes a buffer zone, a reserved zone for future use, an optimum power test zone for optimum power control (OPC), and an information zone where information regarding a data recording/reproducing apparatus or the status of the rewritable optical disk is recorded. The optimum power test zone is not required in the optical disk for data reproduction.
OPC deals with recording user data in the optimum power test zone using various recording powers before the recording and/or reproducing apparatus records the user data on the rewritable optical disk and then determining an optimum recording power.
In the conventional rewritable optical disk, the optimum power test zone of a fixed size is allocated at a fixed location. Thus, it is not possible to include an additional optimum power test zone or increase the size of the optimum power test zone. Since recording characteristics of an optical disk including a plurality of recording layers depend on which recording layer data is recorded first, the optimum power test zone for OPC should be placed in consideration of the recording characteristics of the optical disk. In particular, when the optimum power test zone is allocated in an outer circumferential area of the optical disk, recording characteristics of the outer circumferential area must be considered.
The recording characteristics of the outer circumferential area of the optical disk including a plurality of recording layers are poorer than those of an outer circumferential area of an optical disk having a single recording layer, which must also be taken into consideration. Similarly, when an area for other purposes is allocated in the outer circumferential area of the optical disk in addition to the optimum power test zone, the recording characteristics of the outer circumferential area must be considered.
For an optical disk including two recording layers L1 and L2, recording characteristics of the recording layer L2 depend on whether data has been recorded in the recording layer L1 close to a pick-up unit. In the case of sequential data recording, data is always recorded first in the recording layer L1. When test data is recorded in the optimum power test zone for OPC included in the recording layer L2, a pre-recorded zone should be allocated in the recording layer L1 in advance since the test data must be recorded first in the recording layer L1.
However, the allocation of the pre-recorded zone increases the manufacturing cost of the data recording and/or reproducing apparatus. Hence, whether to allocate the pre-recorded zone and the optimum power test zone for OPC needs to be selectively determined. In this case, the optical disk requires an OPC zone at a predetermined location and an OPC zone that can selectively be used by a drive.
In terms of time, to effectively record data in the outer circumferential area of an optical disk having two recording layers L1 and L2, the position of a middle area in the optical disk may be different from the same position in an optical disk having a single recording layer. In this case, diverse layouts of the optical disk having the two recording layers L1 and L2 are required to allocate the optimum power test zone for OPC in the outer circumferential area.
The same considerations regarding the allocation of the optimum power test zone must be made when a dedicated area for other purposes is allocated in the outer circumferential area of the optical disk.